1. Field
This application relates generally to wireless communication and more specifically, but not exclusively, to access point communication.
2. Introduction
A wireless communication network may be deployed over a defined geographical area to provide various types of services (e.g., voice, data, multimedia services, etc.) to users within that geographical area. In a typical implementation, access points (e.g., corresponding to different cells) are distributed throughout a network to provide wireless connectivity for access terminals (e.g., cell phones) that are operating within the geographical area served by the network.
In some networks, low-power access points (e.g., femtocells) are deployed to supplement conventional network access points (e.g., macro access points). For example, a low-power access point installed in a user's home or in an enterprise environment (e.g., commercial buildings) may provide voice and high speed data service for access terminals supporting cellular radio communication (e.g., CDMA, WCDMA, UMTS, LTE, etc.). In general, these low-power access points provide more robust coverage and higher throughput for access terminals in the vicinity of the low-power access points.
At a given point in time, an access terminal may be served by a given one of these access points. As the access terminal roams throughout the geographical area, the access terminal may move away from its serving access point and move closer to another access point. In addition, signal conditions within a given cell may change, whereby an access terminal may be better served by another access point. In these cases, to maintain mobility for the access terminal, the access terminal may be handed-over from its serving access point to the other access point.
In general, for handing-over an active call user from a source cell to a target cell, the unique cell identity of the target cell has to be known at the source cell. In a planned macrocell deployment, mapping between physical layer identities (such as PSCs in UMTS) and cell identities of the neighboring cells is pre-provisioned by an operator or network infrastructure vendor at each cell for handover purposes. Thus, when an access terminal (e.g., a UE) reports the physical layer identity (e.g., PSC) of a neighboring cell, the source cell uses the provisioned mapping to determine the cell identity and, thereby, initiate handover to the target cell.
In contrast, it may be more difficult to provide a mapping between physical layer identities and cell identities for low-power access point deployments. For example, these deployments are generally unplanned and are allotted a relatively small number of physical layer identities relative to the number of low-power access points. Thus, it is desirable to have low-power access points self-discover this information.
There are several challenges associated with the discovery of such a target cell identity, however. First, in UMTS, pre-Release 9 UE reports do not contain the cell identity of the target cell. Thus, this information cannot be obtained from measurement reports in these cases. Second, a source low-power access point may not be able to detect all of its neighboring low-power access points via a co-located receiver (also known as network listen module or NLM) and thereby decode the broadcast information from those low-power access points for the cell identity information. For example, other relatively nearby low-power access points may be “hidden” from (e.g., not detectable by) a source low-power access point, even though they may be close enough to be seen by (e.g., detectable by) an access terminal within the coverage of the source low-power access point.
Further to the above, there are other reasons why it is desirable for a low-power access point to be able to communicate with its neighbor access points. For example, access points in communication may coordinate on selection parameters such as transmit power and physical layer identifiers and may share identifiers, paging area codes, or other information. In this way, the access points may cooperate to improve service in the area, mitigate interference between access points, facilitate handover of access terminals between access points, and so on. In view of the above, there is a need for effective techniques for enabling communication between access points.